The present invention relates to cathode ray tubes in general, and more particularly, to tubes utilized in the colored television industry.
Colored or polychromatic television tubes employ a shadow mask that is suspended a short distance behind the interior surface of the tube faceplate where the various phosphors are positioned. In order to maintain the distance between the phosphor coated interior surface of the faceplate and the shadow mask, it has been common to fabricate the shadow mask with a heavy frame to minimize distortion and maintain the aforementioned distance better known as the "Q" distance. The shadow mask and its associated frame are held within the faceplate by suspending it from a series of pins or studs which are embedded within the interior glass wall of the faceplate flange.
Since the manufacture of the glass components of a television tube must be done at elevated temperatures, it is difficult to maintain precise dimensional tolerances on, for example, the interior surface of the tube faceplate. The grinding of the faceplate exterior is easily accomplished by various grinding techniques, however, because of the faceplate flanges, the grinding of the faceplate interior is quite difficult. Consequently, the interior of the faceplate retains essentially that configuration imparted upon it by the molds used in its creation. Also, there are certain manufacturing tolerances associated with the fabrication of the shadow mask, as well as certain dimensional changes caused by the cooling of the glass.
The present invention relates to an improvement in the positioning of a shadow mask within the television tube, particularly, television tubes that utilize the new concept of a flexible mask as distinguished from the more rigid masks employing a heavy frame. With the advent of a flexible mask, certain positioning techniques can be used which were not possible with the more rigid prior frames. The method of affixing the shadow mask within the television tube permits the faceplate assembly, including the shadow mask, to be easily and repeatedly installed and removed from its mounts while assuring a degree of accuracy not heretofore attainable.